THE ARABIC ORIGINS OF THE SCIENTIFIC SUNDIAL ( Sometimes called the “Moorish” sundial.) Christopher StJ H Daniel MBE

against the Meccans and, in 631, raised The origins of the sundial are lost in an army for an attack on Mecca. Faced the mists of antiquity; but there is no with such a powerful force, Mecca doubt that the very earliest civilisations surrendered without giving battle. On made use of the shadows of objects to entering the town, Muhammad’s first gauge the time of the day and the act was to turn the Ka’aba shrine of the season of the year. The ancient old religion into the holiest shrine of Eqyptians made use of a device for Islam. The following year, in 632, measuring the length of shadows as Muhammad himself led the people of early as c 1500 BC, whilst the ancient Medina on their pilgrimage to the Greeks had a thorough understanding Ka’aba in Mecca; but, succumbing to of the construction of sundials, albeit ill health, he died on his return home. instruments that indicated unequal or seasonal hours. Nevertheless, the In the hundred years after the death of origin of the construction of the Muhammad, but under his inspiration, scientific sundial, indicating the armies of Islam quickly conquered equinoctial or equal hours, as are in Syria, making Damascus their new use today, in which the style or capital, thence continuing their gnomon of the instrument lies in the conquests, taking Mesopotamia and meridian, in the polar axis of the earth, Persia. Swiftly, their great armies is attributed to the brilliant scientists of spread their religion over vast areas of Islam. the known world, from the borders of China in the east, across North Africa to Morocco and Spain in the west. The Islamic era dates from the Prophet History has named the Muslim Muhammad’s migration (Hejira or conquerors of Spain as Moors, Hijrah) from Mecca (Makkah) to probably because they came via Medina (Al Madīnah) in AD 622. Morocco; but their leaders were Arabs Muhammad (c. AD 570 – 632) was from Damascus, who had gathered born in Mecca, which at that time was their armies from the converted Berber a centre of the Arabian caravan trade, tribes of North Africa. In the spring of in what is now Saudi Arabia. At the the year AD 711, under the command age of 25 he married Khadija, a of Tariq ibn Ziyad, an army of 12,000 wealthy widow who had employed him Muslims crossed the strait between the to conduct a caravan to Syria. About Pillars of Hercules, now the Strait of the year 610, when Muhammad was Gibraltar, and marched north into forty years old, he began receiving the Spain. By 732, they had all but divine revelations, which led to the conquered the Iberian Peninsula and foundation of the religion of Islam; but had crossed the Pyrenees, where, at the authorities in Mecca opposed his last, their advance was halted, near teaching and, such was the increasing Poitiers, in southern France. danger to his person and to his Nevertheless, it took 760 years before followers, that, in 622, he fled some the Christian princes of Spain finally 220 miles north to Medina, where he regained their country in 1492, albeit at settled. Subsequently, he took up arms the cost of the culture that Islam had brought in the wake of its Moorish title of his work, in which the word al- conquests. jabr, i.e. “algebra” appears, is his best claim to fame. (1) In the ensuing relative peace of the Islamic empire, science and art flourished and whilst the Muslim armies had sacked Alexandria in 642 and burnt the great library, the Arabs inherited much that had survived. This included treatises from the famous Greek school of astronomy and, indeed, Ptolemy’s great work, bearing the Arabic name Almajest, owes much to the esteem in which it was held in the new cultural climate of Islam. Many distinguished Arab scientists emerged in the dawn of this Al-Battani (c.AD 850-929.) – Abu- civilisation and mathematical ‘Abdullāh Muhammed Ibn-Jábir Ibn astronomy was one of the disciplines Senán Al-Battáni (Latinized as in which they excelled. However, of ‘Albategnius’) – was born in Batan, in those who were skilled in what is now Iraq; but spent much of mathematical astronomy and who had his life in Damascus. The son of a acquired the knowledge to invent the builder of astronomical instruments, he scientific sundial, the most notable determined the length of the year with included such bright luminaries as Al- remarkable accuracy, the times of the Khw -Battani, Al-Haitham, ārizmī, Al equinoxes and the angle of the tilt of Al-Biruni and the lesser known Aboul the earth’s axis to the plane of its orbit. Hhassan. (2)

Al-Khwārizmī (AD 783 – c.850.) – Al-Haitham (AD 965-1039.) – Abu Abū Jacfar Muhammad ibn Mūsā al- Ali Al-Hasan ibnul Hasan ibn al- Khwārizmī – was born in the sultanate Haitham – (better known as Alhazen in of Khwarizm, probably near the capital the western world) was born in Basra, city of Kath, close to the ancient town in what is now Iraq. Known as “The of Kiva, which lies to the south of the Father of Optics,” Al-Haitham was one Aral Sea, some 620 miles to the north- of the greatest of all scientists that the east of Tehran, in Uzbekistan. world has ever seen. Although he is However, he spent much of his life in famed for his work in optics, he Baghdad, where he studied devoted his spare time to acquiring mathematical astronomy and became knowledge in other fields, including the leading scientist of his day. Lunar mathematics, physics, astronomy and crescent visibility tables are attributed medicine. One of his studies to him, for predicting the sightings of concerned the annual phenomenon of the lunar crescent, in connection with the flooding of the river Nile delta, the regulation of the Islamic lunar when he conceived a scheme for a calendar. He wrote works on the dam, suggesting a site near Aswan. construction of astrolabes and sundials, Invited to Cairo, perhaps about the and compiled tables of coordinates for year AD 1005, by Al-Hakim, the this purpose for horizontal and vertical ruling Caliph, Al-Haitham found the sundials at different latitudes; but the task too daunting with the resources at court. He was evidently allowed to his disposal. Alarmed at the prospect travel and was given official support of a horrible fate, he feigned madness for his work. Thus, he determined the and suffered imprisonment c.1007, latitude of Ghazna – about 75 miles being released only after Al-Hakim’s south of Kabul – observed eclipses, death in AD 1021. Thereafter he demonstrated that the earth was settled for a scholarly life in the spherical, and calculated its radius as University (Jamia) of Al-Azhar in 6,338.80 kilometres. He travelled to Cairo, where he engaged in scientific India, studied Hindu astronomy and pursuits. Apart from his major treatise trigonometry, and wrote an on optics, he also wrote works on such encyclopaedic work India, which he matters as the determination of time completed soon after Sultan Mahmud’s with precision, the determination of the death in AD 1030. His scholarship and meridian, the determination of the output was phenomenal and not the altitude of the celestial pole and least of his works was an exhaustive various treatises on sundials. (3.) treatise on shadows, in which he Al-Biruni (AD 973-c.1050.) – Abu al- describes instruments which employ Rayhān Muhammad ibn Ahmad al- shadows in their operation, including Bīrūnī – was born near Kath, the the astrolabe and the sundial. (4.) capital of the sultanate of Khwarizm, close to Khiva, in what is now Aboul Hhassan of Morocco (c. AD Uzbekistan. Of Persian descent, he 1230.) was an astronomer, about whom was born into a climate of advanced little is known; but who is associated culture; but, evidently orphaned in his with the practical development of infancy, he was fortunate to have a equal or equinoctial hours and the member of the Khwarizmian royal invention of the so-called ‘Moorish’ family, a distinguished mathematician scientific sundial, with its inclined and astronomer, as his foster father. gnomon directed to the celestial pole. Thus, Al-Biruni began studying It is perhaps possible that he was a astronomy and other scientific Moroccan ruler who was the forebear subjects. At the age of 17 he was of Abu al-Hasan, a Moroccan king, making astronomical observations and, who refurbished the 80-foot-high stone from measuring the sun’s meridian tower of the hillside Arab fortress at altitude, with his own self-made Gibraltar in AD 1333. (5.) instrument, calculated the latitude of the city of Kath. Astronomer, There were many bright stars in the mathematician, physicist, geographer, glittering Arabian firmament of science historian, linguist, ethnologist, and art; but these were perhaps the pharmacologist, poet, novelist and brightest of those most able to invent philosopher – Al-Biruni became one of the scientific sundial. Whilst the most brilliant scholars of his age. astronomers evidently used equinoctial He travelled widely, not least because hours in their observations, Islamic he was taken prisoner in 1017 by the religious services were commonly armed hosts of Mahmud of Ghazna, governed by the use of temporal, who overran Khwarizm in that year. seasonal or unequal hours. Thus there Al-Biruni was deported to Ghazna in was no real requirement for a sundial Sijistan, now a part of northern that would indicate equal hours. Afghanistan, where, already famous, Nevertheless, the invention is the brilliant scientist was probably seen attributed to the Arabs and it has been as an enhancement to the sultan’s thought that this form of dial might have been introduced into Christian Europe through the medium of the CAPTIONS: Crusades, or, perhaps more likely, via the established centres of Arabic (1) Al-Haitham – an artist’s learning in Spain. Here it is known impression. that Christian scholars were able to study freely and benefit from the then (2) Al- Biruni – an artist’s tolerant culture of Islam. Thus, the impression. scientific sundial may have reached Germany, in the first place, in the late 14th or early 15th century. However, Previously published in Clocks, August 2008 the question of its origin and its © C StJ H Daniel, 2008. Published with inventor still remains a matter of permission. speculation.

References:

(1.) D. A. King: al- KHWĀRIZMĪ and New Trends in Mathematical Astronomy in the Ninth Century, The Hagop Kevorkian Center for Near Eastern Studies, New York, 1983.

(2.) I. Asimov: Biographical Encyclopedia of Science and Technology, Doubleday & Company, Inc., New York, 1964.

(3.) H. M. Said (Editor): Ibn Al- Haitham: Proceedings of the Celebrations of [the] 1000th Anniversary, Hamdard National Foundation, Pakistan, 1970.

(4.) E. S. Kennedy: The Exhaustive Treatise on Shadows by Abū al- Rayhān Muhammad b. Ahmad al- Bīrūnī, translation and commentary, 2 vols., Institute for the Hisrory of Arabic Science, Aleppo, Syria, 1976.

(5.) C. St J. H. Daniel: Sundials – Instruments of Time, The Proceedings of the Oxford 2000 Convention, The Antiquarian Horological Society, Ticehurst, 2000.